Binary search tree (BST) in Java

gistfile1.java

package test ;

/* educational purpose Binary search tree */
/* @author http://github.com/rjha */

public class bst {

    private Node root ;

    public bst(int x) {
        this.root = this.getNewNode(x) ;
    }

    private class Node {
        public int value ;
        public Node left ;
        public Node right ;

    }

    public Node getRoot() {
        return this.root ;
    }

    private Node getNewNode(int x) {
        String message = String.format("new (%d) \n",x);
        System.out.print(message);
        Node node  = new Node();
        node.value = x ;
        node.left = null ;
        node.right = null ;
        return node ;
    }   


private void addLeftNode(Node parent, int x) {
        String message = String.format("(%d) ->left(%d) \n",parent.value,x);
        System.out.print(message);
        Node node = this.getNewNode(x);
        parent.left = node ;
    }   

    private void addRightNode(Node parent, int x) {
        String message = String.format("(%d) ->right(%d) \n",parent.value,x);
        System.out.print(message);
        Node node = this.getNewNode(x);
        parent.right = node ;
    }   
        

    public void insert(Node node,int x) {
        // @warning node.right and node.left can change between these two lines
        // so either return explicitly or use method scope left/right node.
       
        if(x > node.value && (node.right == null)) { this.addRightNode(node,x); return ;}
        if(x > node.value && (node.right != null)) { this.insert(node.right,x); }

        if(x <= node.value && (node.left == null)) { this.addLeftNode(node,x); return ;}
        if(x <= node.value && (node.left != null)) { this.insert(node.left,x); }

    }   

    public void print_in_order(Node node) {
        if(node == null ) return ;
        if(node != null ){
            print_in_order(node.left);
            System.out.print(node.value + " ");
            print_in_order(node.right);
        }   
    }   

    public static void main(String[] args) {
        bst tree = new bst(5);
        Node root = tree.getRoot();
        tree.insert(root,8);
        tree.insert(root,3);
        tree.insert(root,1);
        tree.insert(root,11);
        tree.print_in_order(root);
        System.out.println();

    }   
}